The foam coating of webs, particularly the foam coating of fabrics which are ultimately constructed into draperies or the like, has been practiced commercially at least since the early 1960's. Millions of yards of foam coated fabrics are produced worldwide every year utilizing procedures such as shown in U.S. Pat. Nos. 4,016,831 and 3,527,654. While acceptable product is readily produced utilizing such procedures, as commercialization has developed and a wider variety of fabric styles have been utilized, several long-standing problems have been intensified.
Exemplary long-standing problems in the fabric foam-coating field have been as follows: The necessity for shutting down the operation when the back up surface over which the fabric passes becomes contaminated with foam, dirt, etc. The introduction of voids or thin-coated portions as a result of fabric portions having increased thickness due to surface effects passing between the back up surface and doctor blade. And, most serious of all, the introduction of voids into the backing due to creases and wrinkles in the fabric agjacent to seams between adjacent lengths of fabric, or such creases or wrinkles within the web lengths which may be caused by prior processes or operations (such as improper tentering or batching up processes or operations).
According to the present invention, it is possible to overcome each of the above-mentioned problems. According to the invention, the down-time of the equipment is substantially reduced by allowing cleaning of the web back up surface during actual operation; the introduction of voids due to specific variations of fabric thickness are substantially eliminated by allowing a "floating" action of the web-doctor blade system; and the introduction of voids due to creases and wrinkles around seams or within the web length is virtually eliminated by removing wrinkles or creases from the fabric, and holding the fabric taut during coating. Thus, according to the present invention, it is possible to increase production while substantially eliminating waste due to improper coating of portions of the fabric.
According to the present invention, the conventional flat bed surface backing up the fabric web is eliminated, and instead a relatively large diameter roller is utilized to provide a back up for the traveling fabric web. The roller rotates about a horizontal axis, and the doctor blade (for controlling foam coating) is placed vertically above and slightly in front of a vertical line passing through the roller axis of rotation. Sidewalls act with the doctor blade and the traveling web to confine a foam pillow, the traveling web picking up foam from the pillow and then passing between the roller periphery and doctor blade, with the blade controlling foam thickness. By replacing the flat stationary bed with a continuously rotating structure, it is possible to continuously clean the back up surface, as by merely placing a brush, scraper, or the like in contact with the roller periphery at an area of the roller periphery not engaging the fabric web. Also, by mounting the doctor blade in such a manner relative to the rotating drum small variations in fabric thickness at particular points (normally due to the presence of nubs or other surface effects on the face of the fabric) can be readily accommodated, while the thickness of the foam coating is still properly controllable.
The present invention also utilizes a slat expander or the like mounted in front of the roller for removing wrinkles or creases from the fabric as it passes toward the roller. The slat expander is located directly adjacent the roller so that the spacing therebetween is not significantly greater than the minimum required to allow passage of seams therebetween. As the fabric passes from the slat expander to the roller peripheral surface, frictional engagement between the roller peripheral surface and the fabric holds the fabric in the wrinkle or crease-free condition imparted by the slat expander as the fabric subsequently passes to the foam pillow and doctor blade. Depending upon the type of fabric, it may be necessary to provide surface manifestations (such as engraved needle points) on the roller periphery to facilitate holding the fabric taut while in engagement with the roller periphery. In this way, the introduction of voids into the foam coating as a result of wrinkles or creases adjacent fabric seams or within the web length is essentially eliminated. Also, it is possible to avoid warp tension wrinkling on lightweight construction to minimize voids in the foam.
It is the primary object of the present invention to provide a method and apparatus for the foam coating of a web to maximize production and minimize waste. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.